An array of high-frequency loudspeakers operating in a specific orientation among a structure of sound reflecting surfaces is very complex. Enclosed rooms for listening to music or a performance present a more or less predictable reflective environment, depending on size, shape, volume, and materials of reflective surfaces. Sound reaching a listener consists of both direct sound and reflected sound delayed by the time it takes for reflected sound to reach a listener. In addition, arrays of loudspeakers are subject to similar conflicts, in that cancellation and addition can occur at certain frequencies, changing the timbre and character of the sound. Comb filtering from closely arranged loudspeakers is a significant problem. These detectable audio effects can seriously affect a listener's appreciation of the sound being reproduced by the loudspeakers. A listener's ears are very sensitive to these small variations. So a loudspeaker system can sound very different at different listening positions or in different rooms.
Operating a loudspeaker system outdoors significantly reduces the problem of reflected sound cancellation and addition. However, specific problems arise in outdoor venues as well.
A significant factor in the operation of a loudspeaker system is the amount of diffusion present in the environment. Clearly, operating a loudspeaker system outdoors can suffer from diffusion and sound deficient at higher frequencies.
Loudspeaker arrays are essential to operation of an effective performance in an outdoor venue. As such, a primary concern is not only providing sufficient numbers of loudspeakers in a central location but also assembling each array so that comb filtering does not significantly affect a listener's appreciation of the sound.
Linear and tightly-arranged arrays are widely used in large-scale venues and arenas. However, the audio output of prior art arrays of high-frequency loudspeakers have been found to be subject to effects comb filtering which is easily heard by listeners. It is well known in the art that for a linear array of loudspeakers to operation at, for instance, a 16 KHz frequency channel without comb filtering, the calculated center to center distances between each loudspeaker may not be greater than 1.1 centimeter so that the sound pressure level can be reduced. It is clearly impossible to construct such an array for loudspeakers effective in large or outdoor venues. Currently, linear arrays of high-frequency loudspeakers are formed with a different shaped horns to provide wave front rectification. The linear arrangement angle of each loudspeaker with respect to its adjacent loudspeaker is modified from a parallel orientation of the loudspeaker axes to greater than 0.75 degrees. The change in orientation is done to produce phase isolation to produce high frequencies without noticeable comb filtering. The problems produced by such changes are that for an angular orientation greater than 5 degrees, a gap between adjacent speakers is created.